Reed switch construction

ABSTRACT

A reed switch construction comprising first and second enclosures formed of conductive material and defining opposing troughs located within surrounding walls. First and second contacts are located within these troughs, and an insulating film is interposed between the respective assemblies of enclosures and contacts. An opening is defined by the film, and engaging portions of the respective contacts are positioned in opposing relationship adjacent this opening whereby the contacts can be moved into engagement when subjected to the influence of a magnetic field. The structure described permits accurate spacing of the contacts since the spacing is controlled by the film thickness.

UnitedSt ates Patent Gaber [4 1 May 23, 1972 [54] REED swrrcn CONSTRUCTION I Primary Examiner-H. 0. Jones [72] Inventor. Martin Gaber, 2301 Greenwood, Wil- Anomeyl McDougan, Hersh & Scott mette, 111. 60091 22 Filed: Mar. 16, 1971 ABSTRACT APPL 124,682 A reed switch construction comprising first and second enclosures formed of conductive material and defining opposing troughs located within surrounding walls. First and second [52] U.S.CI. ..200/166 C, 335/151 contacts are located within these troughs, and an insulating [51 ..H0lh 1/66 film is interposed between the respective assemblies of enclo- [58] Field of Search ..200/ 166 J, 166 C; 335/151, sures and contacts. An opening is defined by the film, and en- 335/154; 29/630 C; 317/101 C, 101 CC g ging portions of the respective contacts are positioned in opposing relationship adjacent this opening whereby the con- [56] References Cited tacts can be moved into engagement when subjected to the influence of a magnetic field. The structure described permits UNITED STATES PATENTS I accurate spacing of the contacts since the spacing is'controlled by the film thickness. 1 3,320,559 5/1967 Momson, ..335/151 3,587,011 6/1971 Kurz ..335/151 15 Clains,8DrawingFigures REED SWITCH CONSTRUCTION.

This invention relates to improved reed switch constructions.

Reed switches are widely used for applications requiring rapid switching, long life, and reliable operation. The switches are normally produced by providing contacts formed in whole or in part of ferromagnetic material. These contacts are then sealed within an enclosure, usually made of glass. The enclosure may be evacuatedso that contamination, air resistance to contact movement, and other environmental influences which could effect the switch operation and life can be minimized.

In manufacturing such switches, the majority of which are quite small, the spacing between engaging portions of the con tact members is a critical factor. The spacing must be large enough to prevent jumping of current which .would occur if the gap were too small. On the other hand, the contact spacing cannot be too great since otherwise the magnet specified for closing the switch may notbe strong enough to accomplish this action. The switch performance is also dependent upon the contact spacing and, therefore, accurate spacing is desired so that the switch characteristics will be predictable.

It is a general object of this invention to provide a reed switch construction which can be manufactured without encountering the problems associated with the manufacture of conventional reed switches.

It is a more specific object of this invention to provide a reed switch construction which is characterized by an assembly of parts of relatively simple design whereby the parts can be inexpensively produced and assembled.

It is a still further object of this invention to provide a reed switch construction which incorporates an extremely simple means for controllingcontact spacing whereby switches having highly predictable operating characteristics can be produced on a large scale basis.

These and other objects of this invention will appear hereinafter and for purposes of illustration, but not of limitation, specific embodiments of the invention are shown in the accompanying drawings in which: 1 7

FIG. I is a longitudinal cross-sectional view of a switch construction manufactured in accordance with the concepts of this invention;

FIG. 2 is a cross-sectional view illustrating a stamping construction employed for producing a contact member;

FIG. 3 is a longitudinal cross-sectional view of an alternative switch design;

FIG. 4 is a longitudinal cross-sectional view of an additional alternative switch design;

FIG. 5 is a front end view of the switch construction shown in FIG. 4;

FIG. 6 is a rear end view of the switch construction shown in FIG. 4;

FIG. 7 is a reduced horizontal sectional view taken about the line 7-7 of FIG. 4; and,

FIG. 8 is a reduced horizontal sectional view of the switch construction shown in FIG. 1.

The switch construction of this invention generally comprises a switch housing formed of first and second enclosures. Each enclosure defines a trough located within surrounding walls and contacts are adapted to be received within each trough. The enclosures and associated contacts are formed into a sandwich assembly with a piece of insulating film being interposed between the respective enclosures and contacts.

The film thickness operates to determine the contact spacing and, therefore, switches can be produced with a readily predictable spacing. The film defines an opening so that the opposing contacts can move into engagement and the extent of this opening will determine the force required for closing the contacts. Thus, the edge of the opening provides a fulcrum for a contact thereby determining the bending force required for moving the contact to engaging position.

The enclosures preferably comprise conductive metal pans. By utilizing conductive pans, the use of the switches is greatly simplified since electrical contact with the exterior of the switch is all that is required to place the switch in a circuit.

The metal can be accurately formed by conventional processes and, therefore, production of the pans is very economical. Furthermore, the use of metal has been found to significantly enhance the performance of the switches from the standpoint of the magnetic action required for operating the switches.

FIGS. 1 and 8 illustrate a switch construction 10 characterized by the features of this invention. This construction includes an upper conductive pan l2 and a lower conductive pan 14. These pans define, respectively, troughs 16 and 18, the troughs being confined within surrounding wall portions as shown at 20 in FIG. 8.

A contact 24 is located within the trough 16, and a similar contact 26 is positioned within the trough 18. Each of these contacts defines a pair of contact fingers 28 which in this embodiment provide redundant switching.

' The thickness of the contacts 24 and 26 may be equal to the depth of the troughs 16 and 18 and they will then lie with their outer surfaces level with the end surfaces 30 of the enclosures. The depth of the troughs can be readily controlled by means of a metal stamping operation. Thus, materials are available which can be formed with great accuracy and which will retain their dimensions after forming whereby the depth of the troughs is highly predictable.

By employing metal pans and a stamping operation, a very effective means for controlling contact spacing is also available. As illustrated in FIG. 2, stamping dies and 82 may be utilized for forming a conductive pan 12. In this instance, the die 80 is provided with a projection 84 and a recess 86 is formed in the die 82. This results in the formation of a projection 88 in the completed pan. As shown in FIG. 1, this projection holds the contact arm 28 away from the bottom wall of the pan. A similar projection 90 is formed in the pan 14 for holding the opposing contact arm 28 away from the bottom wall of the pan 14. It will be appreciated that corresponding projections may be formed on the other side of the pan where bifurcated arms 28 are provided for the contacts 24 and 26.

If desired, an additional set of projections may be formed at 92 to improve the contact between the pans and the contacts. These projections squeeze the respective members together to insure engagement.

The material for forming the contacts 24 and 26 and the film material .34 can be secured in accurate thicknesses. Materials of this type are, however, supplied in standard thicknesses which may not be the most suitable for a particular switch design. Accordingly, it is not possible in all cases to use standard metal and film thicknesses for purposes of achieving a particular contact spacing.

The forming of projections in the walls of the pans does, however, provide a practical means for controlling the contact spacing. Thus, a die can be designed for forming a projection having a particular dimensional relationship with the pan in which the projection is formed. By providing a variety of dies, a variety of dimensional relationships become available. The same contact and film materials can then be employed with pans made from different dies and difierent contact spacing will then be achievable.

The contacts are preferably formed of a spring material and the contacts are located in the pans so that they will bear against the projections 88 and 90. This arrangement also serves to maintain the contact spacing within very accurate limits. Various other means could, of course, be utilized for including the switch in a desired circuit.

The insulating film 34 is interposed between the respective pan and contact assemblies of the switch construction. As best shown in FIG. 8, the film 34 overlies the entire area of each pan with the exception of an opening 36 defined in the film. This opening 36 exposes the respective contact fingers 28.

In constructing a switch, the pans are stamped, and the spring contacts are then simply placed in the troughs of the pans. The insulating film 34 (for example, made of Mylar) is then interposed between the pans to provide a sandwich assembly. Any suitable adhesive can be painted or sprayed on the mating surfaces of the insulating body and Mylar for securing the assembly. A double faced Mylar adhesive strip could also be used. If desired, the assembly can be evacuated or an atmosphere other than air may be introduced through a suitable opening which will thereafter be sealed.

Since insulating film of uniform thickness is readily available, the switch manufacturing can be conducted on a highly reliable basis. Thus, the assembly operations, although very straightforward, will inevitably lead to the production of switches with predictable characteristics since the spacing between contacts is completely controllable by the thickness of the film.

The extent of the opening 36 can be controlled for purposes of determining the magnetic force required for operating the switch. The contact fingers 28 may comprise ferromagnetic spring material (for example Kovar or silicon steel), and the location of the edge 38 of the opening 36 will determine the fulcrum point for spring movement. A stiffer or more flexible switch operation can be very simply obtained by varying the position of the edge 38.

FIG. 3 illustrates a modified form of the invention wherein pans 40 and 42 define troughs 46 and 48 extending over approximately one-half of the body length. The contacts 50 and 52 extend from different ends of the switch into an overlapping relationship. The opening 54 defined by insulating film 56 provides for engagement of the contact ends when the structure is subjected to the influence of a magnetic field. The edges 58 and 60 of the opening 54 provide fulcrum points for the respective spring contacts.

In the modification of the invention shown in FIGS. 4

. through 7, the pans 62 and 64 define troughs 65 and 67. An insulating film 66 is positioned between the peripheral walls of the conductive pans to hold these pans in spaced apart relationship. A single contact 70-is located between the pans, and bifurcated arms 72 are formed in the contact. The end of this contact is held within a gasket 68 which maintains the contact in insulating relationship relative to the conductive pans. The assembly of the contact, film and gasket serves to center the contact between the projections 74 and 76 formed on the interior walls of the pans 62 and 64. The depth of the projections will determine the contact spacing. The switch operation involves swinging movement of the contact arms depending upon the magnetic force applied to the switch. Thus, the contact arms can be made to move between the projections 74 and 76 depending upon the position of an attractingmagnetic field. Electromagnets could, for example be located on opposite sides of the switch and the position of the contact arms will then depend on which magnet is energized.

The switch of FIGS. 4 through 7 includes a tab 78 which extends outwardly between the films 66 and 68 at one end of the construction. Additional leads may then be secured to the pans 62 and 64 to thereby provide for inclusion of the switch in an electrical circuit. The switch of FIGS. 4 through 7 is quite versatile depending upon the functions desired. Where the contact arms are normally centered, then the switch will be open until subjected to a magnetic field. On the other hand, the switch could be normally closed by biasing the contact arms against one of the projections 74 or 76, and then using a magnet to swing the contact arms against the other projection.

The switch structures of this invention are uniquely suitable for attachment on a printed circuit board. By providing exposed contact areas on the surface of the switches, the switch structure can be pushed into an appropriate opening in the printed circuit board. The switch can then be included in the circuit, for example by employing solder, to achieve a connection between the exposed contacts and the conductive areas on the printed circuit board.

The attaching of contacts to the switch construction may be accomplished in various ways including the pressing of contact arms against the switch pans or the soldering of contacts to the housing. After the contacts have been applied, the exposed switch may be dipped or sprayed with an insulating plastic or the like to avoid shorting which could occur if a conductive object were brought into contact with the conductive pans. This insulating technique is particularly suitable where the switch is mounted on a printed circuit board.

The use of conductive pans is of value where the conductive material comprises a nickel-copper alloy (commonly known as ,nickel silver), brass or some other material having relatively high magnetic transparency. Such pans will not significantly affect the force of the magnetic field used for operating the contacts. Thus, the magnetic transparency permits transfer of the magnetic field in a rapid fashion so that the magnetic effect will take place in a very predictable fashion from a timing standpoint. There will be no delay occasioned by magnetic characteristics of the pans, and the location of the magnet is not too critical in view of the fact that the magnetic field will penetrate the pans much like light passes through a window. The pans could also be formed from a non-metallic material but in this case a conductive coating or the like would be necessary to place the pans in an electrical circuit.

In typical embodiments, the pans are made form material 0.01 an inch thick, the contacts from material 0.005 to 0.010 an inch thick and the Mylar or other insulating film from 0.001 to 0.003 an inch thick. Such switches are relatively small and represent a large portion of the market for reed switches. Larger switches are, however, readily manufactured in accordance with the concepts of this invention. In such switches, the relative size of the respective members may be approximately the same, that is, the pans may be approximately twice the thickness of the contacts and approximately four times the thickness of the Mylar. The ratio of the gauss value to the flexural strength is, of course, a factor which must be considered in any design irrespective of the over-all size.

The dimensions of a particular film and contact material will be held constant when producing a batch of switches, and the'switches will then automatically have a constant contact spacing. Where projections are formed, the contact spacing will change for film and contacts of a given thickness. In providing dies for forming the projections, removable inserts may be used as the actual projection forming means to allow for wear and to permit variations within the same dies.

It will be understood that various changes and modifications may be made in the above described structure which provide the characteristics of this invention without departing from the spirit of the invention.

That which is claimed is:

1. A reed switch construction comprising a first conductive enclosure, a second conductive enclosure, an insulating film positioned in overlying relationship with respect to said enclosures, said insulating film defining peripheral portions engaging the surrounding walls of each of said enclosures to thereby maintain the enclosures in spaced apart relationship, contact means positioned within the space defined between said enclosures, said contact means being movable within said space when subjected to magnetic force, an opening defined by said insulating film in the area occupied by an engaging portion of said contact means, and means for securing said enclosures, said contact means and said insulating film in a sandwich-like assembly whereby the space available for movement of the engaging portion of said contact means is determined by the thickness of said insulating film.

2. A construction in accordance with claim 1 wherein said enclosures define first and second troughs located within surrounding walls, said contact means comprising first and second contacts positioned within said troughs, said insulating film being disposed between said contacts to normally hold the contacts out of engagement with each other, each of said contacts defining an engaging portion located within the opening defined by said insulating film whereby magnetic force is adapted to bring said contacts into engagement, and including external leads engaging said enclosures whereby a circuit is completed between said leads when said contacts are brought into engagement.

3. A construction in accordance with claim 2 wherein the depth of said troughs is approximately equal to the thickness of the contacts located within said troughs.

4. A construction in accordance with claim 2 wherein said contacts define a plurality of contact fingers thereby providing redundant engaging portions.

5. A construction in accordance with claim 1 wherein the sandwich assembly is adapted to be plugged into a printed circuit board, said enclosures providing for inclusion of the switch in the circuit associated with the board.

6. A construction in accordance with claim 2 wherein said contacts comprise spring fingers normally pressing against the bottom surfaces of the associated troughs whereby operation of the reed switch necessitates movement of the fingers in opposition to the normal spring action.

7. A construction in accordance with claim 2 wherein the edges of said opening defined by said insulating film engage said contacts at an intermediate point along their lengths, said edges thereby providing a fulcrum determining the bending force required for moving the engaging portions of the contacts together.

8. A construction in accordance with claim 1 wherein said contact means comprises a single contact element positioned between said enclosures, the engaging portion of said element being adapted to swing between the interior walls of the respective enclosures for engagement with said walls depending upon the nature of the magnetic force to which the construction is subjected.

9. A construction in accordance with claim 8 wherein said element includes a terminal portion extending outwardly of said enclosures, and including an insulating gasket for holding the end of said element carrying said terminal portion out of engagement with said enclosures.

10. A construction in accordance with claim 1 including a projection formed on the interior wall of at least one of said enclosures, the engaging portion of said contact means being movable into contact with said projection whereby the movement of said contact means is limited by said projection.

said contact means comprises a pair of contacts and including projections formed in the interior wall of each of said enclosures for engaging said contacts, said projections thereby cooperating with said insulating film for determining the spacing between said engaging portions.

12. A construction in accordance with claim 10 wherein said enclosures each defined a projection and wherein said contact means comprise a single contact element having its engaging portion positioned between said projections, said projections thereby cooperating with said insulating film for determining the allowable movement of said contact element.

13. A construction in accordance with claim 10 wherein said enclosures are formed from a material having magnetic transparency.

14. A method for producing a reed switch construction comprising the steps of forming first and second conductive enclosure members, each of said enclosures defining an interior trough located within surrounding walls, placing a contact within each of said troughs, locating an insulating film in overlying relationship with respect to the surrounding walls and contact of one enclosure, placing the second enclosure and associated contact in overlying relationship relative to said film whereby said enclosures, contacts and film form a sandwichlike assembly, said film defining an opening positioned op posite engaging portions of said contacts whereby said contacts are adapted to move into engagement when said switch is subjected to magnetic force.

15. A method in accordance with claim 14 including the steps of forming a projection on the interior wall of at least one of said enclosures, said projection engaging at least one of said contacts for thereby determining the position of said one contact relative to the other contact. 

1. A reed switch construction comprising a first conductive enclosure, a second conductive enclosure, an insulating film positioned in overlying relationship with respect to said enclosures, said insulating film defining peripheral portions engaging the surrounding walls of each of said enclosures to thereby maintain the enclosures in spaced apart relationship, contact means positioned within the space defined between said enclosures, said contact means being movable within said space when subjected to magnetic force, an opening defined by said insulating film in the area occupied by an engaging portion of said contact means, and means for securing said enclosures, said contact means and said insulating film in a sandwich-like assembly whereby the space available for movement of the engaging portion of said contact means is determined by the thickness of said insulating film.
 2. A construction in accordance with claim 1 wherein said enclosures define first and second troughs located within surrounding walls, said contact means comprising first and second contacts positioned within said troughs, said insulating film being disposed between said contacts to normally hold the contacts out of engagement with each other, each of said contacts defining an engaging portion located within the opening defined by said insulating film whereby magnetic force is adapted to bring said contacts into engagement, and including external leads engaging said enclosures whereby a circuit is completed between said leads when said contacts are brought into engagement.
 3. A construction in accordance with claim 2 wherein the depth of said troughs is approximately equal to the thickness of the contacts located within said troughs.
 4. A construction in accordance with claim 2 wherein said contacts define a plurality of contact fingers thereby providing redundant engaging portions.
 5. A construction in accordance with claim 1 wherein the sandwich assembly is adapted to be plugged into a printed circuit board, said enclosures providing for inclusion of the switch in the circuit associated with the board.
 6. A construction in accordance with claim 2 wherein said contacts comprise spring fingers normally pressing against the bottom surfaces of the associated troughs whereby operation of the reed switch necessitates movement of the fingers in opposition to the normal spring action.
 7. A construction in accordance with claim 2 wherein the edges of said opening defined by said insulating film engage said contacts at an intermediate point along their lengths, said edges thereby providing a fulcrum determining the bending force required for moving the engaging portions of the contacts together.
 8. A construction in accordance with claim 1 wherein said contact means comprises a single contact element positioned between said enclosures, the engaging portion of said element being adapted to swing between the interior walls of the respective enclosures for engagement with said walls depending upon the nature of the magnetic force to which the construction is subjected.
 9. A construction in accordance with claim 8 wherein said element includes a terminal portion extending outwardly of said enclosures, and including an insulating gasket for holding the end of said element carrying said terminal portion out of engagement with said enclosures.
 10. A construction in accordance with claim 1 including a projection formed on the interior wall of at least one of said enclosures, the engaging portion of said contact means being movable into contact with said projection whereby the movement of said contact means is limited by said projection.
 11. A construction in accordance with claim 10 wherein said contact means comprises a pair of contacts and incluDing projections formed in the interior wall of each of said enclosures for engaging said contacts, said projections thereby cooperating with said insulating film for determining the spacing between said engaging portions.
 12. A construction in accordance with claim 10 wherein said enclosures each defined a projection and wherein said contact means comprise a single contact element having its engaging portion positioned between said projections, said projections thereby cooperating with said insulating film for determining the allowable movement of said contact element.
 13. A construction in accordance with claim 10 wherein said enclosures are formed from a material having magnetic transparency.
 14. A method for producing a reed switch construction comprising the steps of forming first and second conductive enclosure members, each of said enclosures defining an interior trough located within surrounding walls, placing a contact within each of said troughs, locating an insulating film in overlying relationship with respect to the surrounding walls and contact of one enclosure, placing the second enclosure and associated contact in overlying relationship relative to said film whereby said enclosures, contacts and film form a sandwich-like assembly, said film defining an opening positioned opposite engaging portions of said contacts whereby said contacts are adapted to move into engagement when said switch is subjected to magnetic force.
 15. A method in accordance with claim 14 including the steps of forming a projection on the interior wall of at least one of said enclosures, said projection engaging at least one of said contacts for thereby determining the position of said one contact relative to the other contact. 